Demands for wireless communication significantly increase in recent years and a plurality of different wireless communication standards compete with one another, and so there are circumstances where a plurality of wireless communication systems according to various types of services are mixed. Under these circumstances, it is increasingly demanded that, by adding multimode functions that enable one terminal station or base station to support a plurality of wireless communication standards, an environment for seamless connection is provided and the efficiency in product development improves.
As a configuration example that enables one wireless communication terminal to support a plurality of wireless communication standards, for example, Patent Documents 1 and 2 disclose a configuration for, for example, separately providing wireless communication processing sections respectively corresponding to the supporting wireless communication standards and controlling switching to a desired processing sequence when necessary. On the other hand, as another configuration, for example, Patent Document 3 already disclosed a configuration using a software radio processing technique of changing wireless communication processing functions by switching function description of, for example, software.
A configuration example of a conventional multimode wireless communication terminal will be described later using FIG. 1 and FIG. 2. In FIG. 1, standard A wireless communication processing section 4001a that carries out wireless communication processing supporting wireless communication standard A and standard B wireless communication processing section 4001b that carries out wireless communication processing supporting wireless communication standard B, are connected with switching controlling section 4002. Switching controlling section 4002 selects and switches communication sequences for carrying out wireless communication according to a condition of a communication link of each wireless communication standard and a request from a user or an application, and connects data input/output terminals between the selected wireless communication processing sequence and upper layer processing section 4003. In this way, communication is carried out by selecting and switching desired wireless communication processing sequences when necessary, so that a wireless communication terminal is able to carry out communication supporting a plurality of wireless communication standards.
FIG. 2 shows a configuration example of a multimode wireless communication terminal that uses the software radio processing technique. In FIG. 2, standard A analogue signal processing section 4004a including a processing section that carries out analogue signal processing and a conversion of analogue signals into digital signals in wireless communication processing supporting wireless communication standard A, and standard B analogue signal processing section 4004b including a processing section that carries out analogue signal processing and a conversion of analogue signals into digital signals in wireless communication processing supporting wireless communication standard B, are connected with digital signal processing section 4005. Digital signal processing section 4005 is able to change the details of signal processing by changing software description of, for example, programs. Digital signal processing section 4005 carries out digital signal processing by switching the details of signal processing between digital signal processing supporting wireless communication standard A and digital signal processing supporting wireless communication standard B according to control by switching control section 4006, supplies data after reception processing, to upper layer processing section 4007, carries out digital transmission signal processing on transmission data supplied from upper layer processing section 4007 and then outputs transmission data to an analogue signal processing section supporting a desired wireless communication standard. In this way, software description of, for example, programs, supporting a desired wireless communication standard is changed when necessary, and communication functions are switched, so that one wireless communication terminal is able to carry out communication supporting a plurality of wireless communication standards.
On the other hand, a filter processing section, particularly, a digital filter processing section, which is one of functions required to select desired band signals upon wireless communication processing, is focused upon. To realize multimode functions as described above, functions are required to enable flexible change of characteristics such as frequency response characteristics according to different required specifications of the applicable wireless communication standards. In this way, for example, Patent Document 4 and Patent Document 5 already disclosed configurations for flexibly changing tap coefficients and operation modes in a digital filter. Patent Document 4 discloses a configuration and operation example of providing components of a plurality of adders, multipliers, delayers and registers at predetermined positions, forming these components with data bus line groups for switching connection between input/output terminals of each component and switching circuits for switching connection between these components, and setting an arbitrary digital filter. Further, Patent Document 5 discloses a configuration and operation example of changing the tap coefficients of a filter at random and switching processing types of a filter between serial and parallel when necessary.    Patent Document 1: Japanese Patent Application Laid-Open No. HEI10-174169 (page 3 to 4 and FIG. 1)    Patent Document 2: Japanese Patent Application Laid-Open No. 2002-190769 (page 6 and FIG. 4)    Patent Document 3: Japanese Patent Application Laid-Open No. 2004-153661 (page 6 and FIG. 4)    Patent Document 4: Japanese Patent Application Laid-Open No. SHO63-252009 (page 2 to 4 and FIG. 1)    Patent Document 5: Japanese Patent No. 2520451 (page 2 to 5 and FIG. 1)